Arrangement to produce electrical signals through affecting a magnetic circuit



Aug. 25, 1959 F. H. MITTAG 2,901,676

ARRANGEMENT TO PRODUCE ELECTRICAL SIGNALS THROUGH AFFECTING A MAGNETICCIRCUIT Filed March 15, 1955 O N C i I Rel a R R a United States PatentARRANGEMENT TO PRODUCE ELECTRICAL SIG- gAls THROUGH AFFECTING A MAGNETICIR UIT Fritz H. Mittag, Berlin-Friedman, Germany, assignor toInternational Standard Electric Corporation, New York, N.Y., acorporation of Delaware Application March 15, 1955, Serial No. 494,440

Claims priority, application Germany March 16, 1954 3 Claims. (Cl.317-150) Certain arrangements, in particular railroad safety systems,arrangements to control conveying plants such as pneumatic displatchtube systems, devices to count railway cars, and still otherarrangements employ a magnetic circuit which is affected by aferromagnetic body applied to this circuit or moved past it. If thisbody is displaced into a position in which it is in such a closeproximity to the magnetic circuit as to vary the magnetic flux, thencertain effects on the circuit can be produced. The magnetic circuit iscoupled to electric circuits which in accordance with that influence onthe magnetic circuit produce electrical signals by means of suitableswitching elements.

The invention concerns arrangements of this type. These employ a chokewhose iron core is included in the magnetic circuit while its winding isincluded in the electric circuit.

Such an arrangement is shown in the accompanying drawing.

The magnetic circuit is constituted by the iron core of the choke Dr andby two limbs A, B. The free ends of these limbs have an air gap Lbetween them. If body K, magnetized in its longitudinal direction, ismoved toward the air gap L then the inductance of the choke Dr will bevaried thereby. Choke Dr then constitutes an element of a circuit fedwith alternating voltage. The other elements of the circuit areconstituted by choke Dr' and resistors R1, R2. These resistors areconnected in parallel with condensers C1, C2 and in series withrectifiers G1, G2. In parallel with the resistors R1, R2 there isarranged the coil of a relay Rel. To the outer points of theseries-connected chokes Dr and Dr there is connected the source ofalternating voltage.

This arrangement acts as follows:

At first the inductances of the chokes are the same and the circuit isin the state of equilibrium. The circuit is initially maintained inequilibrium because the alternating current impedance of the chokes Dr,Dr remains equal. This impedance is high and alternately negativehalf-cycles from the source pass through the full wave rectifier networkpresented by rectifiers G1, G2. Under these conditions the condensersC1, C2 charge to the same value and there is no potential difierencebetween their junctions and their associated rectifiers suflicient tooperate the relay Rel. If the magnetic circuit A, Dr, B is aifected bythe body K, the inductance of choke Dr varies, whereby the equilibriumof the circuit is disturbed and relay Rel hence pulls up. The circuit isunbalanced because the lower impedance of choke Dr affects the chargingcircuit represented by rectifier G1, resistor R1 and condenser C1. Thevoltage across this circuit will be less than the voltage across thecorresponding circuit represented by rectifier G2, resistor R2 andcondenser C2. Condenser C2 will therefore charge to a higher value thancondenser C1 and a current will flow through the relay Rel, and whichrelay is serially connected to the condensers. Positive half-cycles fromthe source will 2,901,676 Patented Aug. 25, 1959 not flow through therectifiers G1, G2 but will flow through the series chokes Drl, Drbecause their impedance is lower than the high impedance to the positivecycles presented by the rectifiers. If the rectifiers are poled in theopposite direction the system will be operative on the positivehalf-cycles. The direction of the magnetization of body K has no effecton relay Rel. This relay pulls up, but where polarized relays areemployed, a definite direction of the energy flow in their circuitry cannow be obtained from the direction of the magnetization of body K.

The invention therefore proposes that the magnetic circuit be given apre-magnetization. To achieve this, a magnet M is included in themagnetic circuit at a suitable place thereof. Preferably, magnet M isfitted to the iron core of the choke Dr. This magnet may be a permanentmagnet or may be excited by means of a directcurrent electric field. Ifnow the circuit is restored to its state of equilibrium and the body Kso displaced as to be near to the air gap L, then this body acts toeither increase or decrease the magnetic flux. Thereby the equilibriumis disturbed in respect of a definite energy direction and the polarizedrelay Rel, operated by current of a pre-determined direction, acts toproduce definite signals.

Thus, in distinction from prior arrangements the inventive circuitrypermits of producing different signals by choosing adequately thedirection of the flux effective in body K. These signals may serve tocontrol routing switches of a transmission path, but also alarm devicesand other safety systems as well as counting arrangements may beoperated in this way.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is:

1. In an electric signalling device, a source of alternating current,first and second circuits each comprising a rectifier, an inductance anda resistance, means for applying current from said source to said firstand second circuits, a polarized load device connected in a thirdcircuit including in series connection said resistances of said firstand second circuits, a core of magnetic material associated with saidinductance of said first circuit, a permanent magnet member adapted tobe moved into proximity with said core to change the equilibrium of saidfirst and second circuits, and means for premagnetizing said core in apredetermined direction whereby said polarized load device will respondonly when the magnetic field of said permanent magnet member has apredetermined direction relative to the direction of the field set up insaid core by said premagnetizing means.

2. Signalling device according to claim 1, in which said premagnetizingmeans comprises a permanent magnet attached to said core.

3. Signalling device according to claim 1, in which said core hasattached thereto a pair of limbs, the free ends of which form an air gapadapted to be bridged by said permanent magnet member.

References Cited in the file of this patent UNITED STATES PATENTS2,609,433 Goff Sept. 2, 1952 2,617,864 Johnson Nov. 11, 1952 2,732,505Walker Jan. 24, 1956 2,753,494 McLellan July 3, 1956 2,802,170 StarrAug. 6, 1957

